[sdiy] Prophet 5 -15v rail is shorting... Need advice

[Barry Klein]

I would wonder what would create high ripple on the supply.
Tantalums should be fine.  Heck, we use em on disk drives... tell me about
ripple...
Feel the electrolytic cap itself in use to see if it is getting hot.
I just got one of those pc fan controllers that had electrolytic caps all
over and they were blowing up and failing/getting hot.  Poor design (extreme
ripple if you put it across the PWM output!), under rated caps.
Could be there is a bad ground in the supply circuit or a bad regulator.  It
may be oscillating etc.  A more tolerant cap may just be covering up the
problem.

Barry


-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Gil W.
Sent: Wednesday, November 07, 2007 8:23 AM
To: GRAHAM ATKINS
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Prophet 5 -15v rail is shorting... Need advice

I asked myself the same question - does any problem
actually *exist* or is the tantalum just not good
enough for this task ? I think the original cap was a
10uf/10v tantalum...



--- GRAHAM ATKINS <gatkins at blueyonder.co.uk> wrote:

> David,
> 
> The electrolytic may be more tolerant than the
> tantalum but
> the underlying problem with high ripple off the
> rectifier may still
> be there, are you sure it is OK to connect to the
> rest of the circuits.
> Are you just covering up the problem ?
> 
> Graham
> On Nov 7, 2007, at 9:46, Gil W. wrote:
> 
> > Hi,
> >
> > The problem has been solved by replacing the tant.
> > with regular 10uf/50v cap...
> >
> > Thanks all !
> >
> >
> > --- "Cornutt, David K"
> <david.k.cornutt at boeing.com>
> > wrote:
> >
> >> Possibly either the rectifier has an open diode,
> >> or something else is causing the supply rail to
> >> oscillate.
> >> Tantalums don't like a lot of ripple current.
> >>
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> 
> 


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